Evaluation of silver nanoparticles attached to methylene blue as an antimicrobial agent and its cytotoxicity

Antibiotic resistance is a great public health challenge of our time. In this work, we have synthesized silver nanoparticles (Ag NPs) using pulsed liquid ablation in different medium of growth and later combined with methylene blue (MB) to evaluate its potential as an effective photodynamic therapy agent. Ag NPs were synthesized by pulsed laser ablation technique in Polyvinylpyrrolidone (PVP), citrate, and Polyvinyl alcohol (PVA). The Ag NPs were characterized using transmission electron microscopy (TEM), UV-Visible (UV-Vis), and photoluminescence (PL) spectra. Next, Ag NPs were coupled with MB and used to deactivate the Gram-negative bacteria, Escherichia coli (E. coli), and Gram-positive bacteria, Staphylococcus aureus (S. aureus). MB and Ag NPs mixture exhibited a synergistic activity and was more effective compared to separate use of MB and Ag NPs. Ag NPs in PVP was shown to be the most effective media for bacterial deactivation. Given the concern for Ag NPs' cytotoxicity for adverse health effect, cytotoxicity measurement in HEK 293T cell lines were performed. Our results show that Ag NPs do not exhibit cytotoxicity up to 50 µg/ml in each solution. Ag NPs/ MB combination has potential to be used in PDT where standard photosensitizers have limitations.